Method and apparatus for beam-space multi-input multi-output transmission based load-modulation

Abstract

A method and an apparatus for beam-space multi-input multi-output (MIMO) transmission based load-modulation are disclosed. The apparatus for beam-space MIMO transmission includes: a plurality of impedance loading circuits each including a plurality of imaginary number impedance elements; a beam-space MIMO control unit calculating loading values of the plurality of imaginary number impedance elements in response to a spatial multiplexing signal; and an RF chain unit generating a first signal having a predetermined carrier frequency.

What is claimed is: 
     
         1 . A beam-space MIMO transmission apparatus comprising:
 a first impedance loading circuit connected to a first antenna element and including a plurality of first imaginary number impedance elements;   a second impedance loading circuit connected to a second antenna element and including a plurality of second imaginary number impedance elements;   a beam-space multi-input multi-output (MIMO) control unit receiving a spatial multiplexing signal for beam-space MIMO and calculating and setting loading values of the plurality of first and second imaginary number impedance elements in response to the spatial multiplexing signal; and   a radio frequency (RF) chain unit generating a first signal having a predetermined carrier frequency and amplifying the first signal and transmitting the amplified first signal to the first and second impedance loading circuits.   
     
     
         2 . The apparatus of  claim 1 , wherein:
 the first impedance loading circuit includes only the plurality of first imaginary number impedance elements, and   the second impedance loading circuit includes only the plurality of second imaginary number impedance elements.   
     
     
         3 . The apparatus of  claim 1 , wherein:
 the first impedance loading circuit includes only the plurality of first imaginary number impedance elements and a first transmission line connected to the plurality of first imaginary number impedance elements; and   the second impedance loading circuit includes only the plurality of second imaginary number impedance elements and only a second transmission line connected to the plurality of second imaginary number impedance elements.   
     
     
         4 . The apparatus of  claim 1 , wherein
 the beam-space MIMO control unit control unit includes:   a beam-space mapping unit calculating current introduced into the first antenna element and the second antenna element by considering information on the spatial multiplexing signal; and   a load modulator control unit calculating loading values of the plurality of respective antenna elements by using the calculated current.   
     
     
         5 . The apparatus of  claim 4 , wherein
 the beam-space mapping unit calculates the current by further considering information on basis beams orthogonal to each other and information on geometrical structures of the first and second antenna elements.   
     
     
         6 . The apparatus of  claim 1 , wherein
 the first signal is a sine wave having a fixed size and a fixed phase.   
     
     
         7 . The apparatus of  claim 6 , wherein
 the RF chain unit includes:   an oscillator generating the first signal; and   a power amplifier amplifying the first signal.   
     
     
         8 . The apparatus of  claim 1 , wherein
 the plurality of first imaginary number impedance elements have a pi-type structure, and   the plurality of second imaginary number impedance elements have the pi-type structure.   
     
     
         9 . The apparatus of  claim 1 , wherein
 the plurality of first imaginary number impedance elements have a T-type structure, and   the plurality of second imaginary number impedance elements have the T-type structure.   
     
     
         10 . A beam-space multi-input multi-output (MIMO) transmission method generating a beam-space signal by modulating loads connected to a plurality of antenna elements, respectively, the method comprising:
 providing a plurality of imaginary number impedance elements to each of the plurality of antenna elements;   generating a spatial multiplexing signal with respect to a plurality of data streams;   calculating loading values of the plurality of imaginary number impedance elements in response to the spatial multiplexing signal;   setting the calculated loading values in the plurality of imaginary number impedance elements; and   generating a first signal having a predetermined carrier frequency and transmitting the generated first signal to the plurality of antenna elements and the plurality of imaginary number impedance elements.   
     
     
         11 . The method of  claim 10 , wherein
 the calculating of the loading values includes:   calculating current introduced into the plurality of antenna elements by using the spatial multiplexing signal; and   calculating loading values of the plurality of imaginary number impedance elements by using the calculated current.   
     
     
         12 . The method of  claim 10 , wherein
 the first signal is a sine wave having a fixed size and a fixed phase which do not vary according to the spatial multiplexing signal.   
     
     
         13 . The method of  claim 10 , wherein
 the load is constituted by only the plurality of imaginary number impedance elements.   
     
     
         14 . A beam-space MIMO base station, comprising:
 a compact antenna unit including a plurality of antenna elements;   a plurality of impedance loading circuits including a plurality of imaginary number impedance elements connected to the plurality of antenna elements, respectively;   a baseband unit generating a spatial multiplexing signal with respect to a plurality of data streams corresponding to the plurality of antenna elements;   a beam-space MIMO control unit calculating loading values of the plurality of imaginary number impedance elements in response to the spatial multiplexing signal and setting the calculated loading values in a plurality of impedance loading circuits; and   an RF chain unit generating a first signal having a predetermined carrier frequency and transmitting the generated first signal to the plurality of impedance loading circuits.   
     
     
         15 . The base station of  claim 14 , wherein
 each of the plurality of impedance loading circuits is constituted by only the plurality of imaginary number impedance elements without a resistance component.   
     
     
         16 . The base station of  claim 14 , wherein
 the beam-space MIMO control unit includes:   a beam-space mapping unit calculating current introduced into each of the plurality of antenna elements by considering information on the spatial multiplexing signal, information on basis beams orthogonal to each other, and information on a geometrical structure of the compact antenna unit; and   a load modulator control unit calculating the loading values of the plurality of imaginary number impedance elements by using the calculated current.   
     
     
         17 . The base station of  claim 14 , wherein
 the first signal is a sine wave having a fixed size and a fixed phase which do not vary according to the spatial multiplexing signal.   
     
     
         18 . The base station of  claim 14 , wherein
 the plurality of imaginary number impedance elements have a pi-type structure or a T-type structure.   
     
     
         19 . The base station of  claim 14 , wherein
 the plurality of antenna elements are positioned at a distance that is smaller than a half-wavelength separation distance from each other.